M42 EXTENSION TUBE This is an auto extension tube set that supports automatic aperture control. By attaching rings of different lengths (1-3) between the lens and the camera, you can change the close-up magnification. ASAHI PENTAX JAPAN Mount: M42 mount. It should be usable with most M42 screw mount lenses, not just Pentax. This will broaden your photographic possibilities. Although the model is old, it is a beautiful and valuable item. There are no noticeable scratches on the extension rings or the case; they are clean.